1. Field of the Invention
The present invention relates to laboratory incubators, and more particularly to a laboratory incubator having an improved temperature control assembly that more effectively maintains the temperature within the incubator in a desired range and that more accurately controls the rate of heat loss from the incubator as ambient temperatures rise.
2. Description of the Prior Art
The temperature within a laboratory incubator must be maintained within a certain operating temperature range that is typically above ambient temperatures. Therefore, it is common to provide laboratory incubators with heating devices that are periodically cycled to maintain the temperature within the interior of the incubators in this range. Heaters can effectively maintain the temperature within a desired range as long as the ambient temperature around the incubator is substantially lower then the desired operating range. However, when the ambient temperature increases so that it approaches the desired operating temperature of the incubator, the rate of heat loss through the walls of the incubator decreases so that excess heat from the chamber does not dissipate therefrom. Typically, if ambient temperatures rise to within 5.degree. C. of the incubator's desired operating temperature, the internal temperature within the incubation chamber begins to rise at the same rate of change as the ambient temperature, causing the temperature within the incubator to rise above its desired operating range.
Prior art attempts to solve this problem include the placement of a jacket of cooling liquid or refrigerant around an incubator. When the ambient temperature rises to a certain high level, the liquid in the jacket is cooled by cooling coils to increase the incubator's heat loss so that the temperature within the incubator can be more easily maintained in a desired range. These prior art cooling devices are impractical and sometimes ineffective, however, because they are expensive, bulky, and difficult to control.
Therefore, there is a need for a laboratory incubator having an improved temperature control assembly for more accurately maintaining the operating temperature within the incubator in a desired operating range and for maintaining a minimum heat loss rate from the incubator as the ambient temperature around the incubator rises.